1. Field of the Invention
The present invention relates to a magnetic film having a high saturated magnetic flux density used in a recording head and a magnetic reproducing head of a hard disk drive (HDD), a magnetic sensor such as a magnetic impedance sensor, and a magnetic circuit component such as a magnetic coil and an inductor; a method for producing the magnetic film; and a thin film head using the magnetic film.
2. Description of the Related Art
In recent years, the maximum recording frequency of HDDs has remarkably increased to about 200 MHz. Furthermore, high-density recording media are likely to have a high coercivity. Therefore, there has been a demand for a recording head material which has a high effective magnetic permeability even at a high frequency and in which a magnetic pole is unlikely to be saturated (i.e., a recording head material which has a high resistivity (high xcfx81), strong uniaxial anisotropy, and a high saturated magnetic flux density (high Bs)).
In order to satisfy the above-mentioned demand, Fxe2x80x94N type material such as FeCrN (J. Appl. Phy. 81(8), Apr. 15, 1997) and FeRhN (IEEE Trans. Magn. VVOl 133. No. 5, 1997) formed by sputtering has been reported as a materiel, for example, with Bs of 2 T (tesla) or more.
The above-mentioned material with high Bs has a low resistivity; therefore, it is difficult to use such material at a high frequency. However, it has been reported that such material is used with a non-magnetic insulator (Al2O3, SiO2, etc.) so as to suppress an eddy current loss (The Japan Society of Applied Magnetics, document of The 103 th Research Institute, p. 2, 1998).
As shown in FIG. 40, U.S. Pat. Nos. 5,543,989 and 5,686,193 disclose a magnetic film with magnetic pole end regions 119 and 123, including a layered structure of a seed layer of sendust and a bulk layer of sendust.
As material for a single layer with high xcfx81, Fexe2x80x94Mxe2x80x94O (M=Hf, Zr) (Summary of the lecture in the 122 nd Japan Society of Metal, p. 179 (424) 1998) is known; however, it has a disadvantage of low Bs. It is required that the above-mentioned material with high Bs or high xcfx81 is capable of providing uniaxial anisotropy and suppressing a ferromagnetic resonance loss. For this purpose, heat treatment in a magnetic field or film formation in a magnetic field is conducted.
However, even in the case where uniaxial anisotropy is given to a conventional film with high Bs, a recording magnetic pole used in a thin film head has an increased aspect ratio between the thickness and the width of a magnetic pole due to a decreased width of a track. Therefore, magnetic anisotropy is caused by an anti-magnetic field in a direction perpendicular to the surface of a recording gap between an upper magnetic pole and a lower magnetic pole.
Because of the above, the direction of a magnetization easy axis shifts in the direction perpendicular to the film surface, which complicates a domain structure in the entire magnetic pole. As a result, magnetic characteristics at a high frequency degrade.
Furthermore, in the case where a magnetic pole is formed by a layered structure including a conventional layer with high Bs and an insulation resistant layer, it is required that at least two sources for supplying material are used for forming the layer with high Bs and the insulation resistant layer, and that these layers are alternately formed, which results in a longer period of time of film formation.
Furthermore, in performing a dry etching technique for minute processing (i.e., patterning of a magnetic pole), an etching rate of a magnetic material of transition metal such as Fe, Co, and Ni is substantially different from that of a non-magnetic insulating material such as Al2O3 and SiO2. Thus, for example, in the case where radical etching or reactive ion etching (RIE) with a high etching rate is conducted, since these reactions are isotropic, unevenness is formed on cross-sections of the magnetic layer and the non-magnetic insulating layer. Furthermore, when reactive gas to be used for each layer is varied, a processing speed as a whole is decreased due to gas substitution, and a device becomes complicated.
Furthermore, in the case where the above-mentioned film is used in high-frequency recording, a spin valve film is used for a reproducing head. At least one of the magnetic layers included in the spin valve film is a fixed layer whose magnetization is fixed in a direction of medium magnetization, and the direction of fixed magnetization is orthogonal to the direction of uniaxial anisotropy required for a recording magnetic pole film for a high frequency.
The recording magnetic film which has been conventionally developed is produced while uniaxial anisotropy is obtained. Alternatively, after the recording magnetic film is produced, uniaxial anisotropy is formed by heat treatment in a magnetic field. Therefore, anisotropy of the recording magnetic film is weakened due to the heat treatment in a magnetic field conducted for fixing the fixed layer of the spin valve film in a preferable direction of the fixed magnetization.
Furthermore, when an upper magnetic pole is formed, the quality of a slope portion degrades due to oblique formation.
A magnetic film of the present invention includes a magnetic layer and an intermediate layer alternately formed, wherein the magnetic layer has a composition represented by (M1xcex11X1xcex21)100xe2x88x92xcex41A1xcex41 (where xcex11, xcex21, and xcex41 represent % by atomic weight; M1 is at least one magnetic metal selected from the group consisting of Fe, Co, and Ni; X1 is at least one selected from the group consisting of Mg, Ca, Sr, Ba, Si, Ge, Sn, Al, Ga, and transition metals excluding the M1; and A1 is at least one selected from the group consisting of O and N), the magnetic layer has the following composition range:
0.1xe2x89xa6xcex21xe2x89xa612
xcex11+xcex21=100
0 less than xcex41xe2x89xa610
the intermediate layer has a composition represented by (M2xcex12X2xcex22)100xe2x88x92xcex42A2xcex42 (where xcex12, xcex22, and xcex42 represent % by atomic weight; M2 is at least one magnetic metal selected from the group consisting of Fe, Co, and Ni; X2 is at least one selected from the group consisting of Mg, Ca, Sr, Ba, Si, Ge, Sn, Al, Ga, and transition metals excluding the M1; and A2 is at least one selected from the group consisting of O and N), the intermediate layer has the following composition range:
0.1xe2x89xa6xcex22xe2x89xa680
xcex12+xcex22=100
xcex41xe2x89xa6xcex42xe2x89xa667
In one embodiment of the present invention, the X1 contains at least one selected from the group consisting of Si, Al, Ti, and V.
In another embodiment of the present invention, M1=M2 and X1=X2.
In another embodiment of the present invention, A2 contains O.
In another embodiment of the present invention, assuming that an average thickness of the magnetic layer is T1 and an average thickness of the intermediate layer is T2, the following expressions are satisfied:
2 nmxe2x89xa6T1xe2x89xa6150 nm
0.4 nmxe2x89xa6T2xe2x89xa615 nm
1xe2x89xa6T1/T2xe2x89xa650
In another embodiment of the present invention, the magnetic film satisfies the following expressions:
20 nm less than T1xe2x89xa6150 nm
1 nm less than T2xe2x89xa615 nm
4xe2x89xa6T1/T2xe2x89xa650
at least 50% of magnetic crystal grains included in the adjacent magnetic layers via the intermediate layer spread across the intermediate layer.
A magnetic film of the present invention includes a magnetic layer and an intermediate layer alternately formed, wherein the magnetic layer has a composition represented by (M1xcex11X1xcex21)100xe2x88x92xcex41A1xcex41 (where xcex11, xcex21, and xcex41 represent % by atomic weight, M1 is at least one magnetic metal selected from the group consisting of Fe, Co, and Ni; X1 is at least one selected from the group consisting of Mg, Ca, Sr, Ba, Si, Ge, Al, Ga, and transition metals including a IVa group, a Va group, and Cr; and Al is at least one selected from the group consisting of O and N), the magnetic layer has the following composition range:
0.1xe2x89xa6xcex21xe2x89xa612
xcex11+xcex21=100
0xe2x89xa6xcex41xe2x89xa610
the intermediate layer has a composition represented by (M2xcex12X2xcex22)100xe2x88x92xcex42A2xcex42 (where xcex12, xcex22, and xcex42 represent % by atomic weight, M2 is at least one magnetic metal selected from the group consisting of Fe, Co, and Ni; X2 is at least one selected from the group consisting of Mg, Ca, Sr, Ba, Si, Al, Ga, Ge, and transition metals including a IVa group, a Va group, and Cr; and A2 is at least one selected from the group consisting of O and N), the intermediate layer has the following composition range:
0.1xe2x89xa6xcex22xe2x89xa680
xcex12+xcex22=100
xcex41 less than xcex42xe2x89xa667
In one embodiment of the present invention, the X1 contains at least one selected from the group consisting of Si, Al, Ti, and V.
In another embodiment of the present invention, M1=M2 and X1=X2.
In another embodiment of the present invention, A2 contains O.
In another embodiment of the present invention, assuming that an average thickness of the magnetic layer is T1 and an average thickness of the intermediate layer is T2, the following expressions are satisfied:
2 nmxe2x89xa6T1xe2x89xa6150 nm
0.4 nmxe2x89xa6T2xe2x89xa615 nm
1xe2x89xa6T1/T2xe2x89xa650
In another embodiment of the present invention, the magnetic film satisfies the following expressions:
20 nm less than T1xe2x89xa6150 nm
1 nm less than T2xe2x89xa615 nm
4xe2x89xa6T1/T2xe2x89xa650
at least 50% of magnetic crystal grains included in the adjacent magnetic layers via the intermediate layer spread across the intermediate layer.
A magnetic film of the present invention includes a magnetic layer and an intermediate layer alternately formed, wherein the magnetic layer has a composition represented by (M1xcex11X1xcex21Z1xcex31)100xe2x88x92xcex41A1xcex41 (where xcex11, xcex21, xcex31, and xcex41 represent % by atomic weight; M1 is at least one magnetic metal selected from the group consisting of Fe, Co, and Ni; X1 is at least one selected from the group consisting of Mg, Ca, Sr, Ba, Si, Al, Ga, Ge and transition metals including a IVa group, a Va group, and Cr; Z1 is at least one selected from the group consisting of Zn, Rh, Ru, and Pt; and A1 is at least one selected from the group consisting of O and N), the magnetic layer has the following composition range:
0.1xe2x89xa6xcex21xe2x89xa612
0.1xe2x89xa6xcex31xe2x89xa68
xcex11+xcex21+xcex31=100
0xe2x89xa6xcex41xe2x89xa610
the intermediate layer has a composition represented by (M2xcex12X2xcex22Z2xcex32)100xe2x88x92xcex42A2xcex42 (where xcex12, xcex22, xcex32, and xcex42 represent % by atomic weight, M2 is at least one magnetic metal selected from the group consisting of Fe, Co, and Ni; X2 is at least one selected from the group consisting of Mg, Ca, Sr, Ba, Si, Al, Ga, Ge, and transition metals including a IVa group, a Va group, and Cr; Z2 is at least one selected from the group consisting of Rh, Ru, and Pt; and A2 is at least one selected from the group consisting of O and N), the intermediate layer has the following composition range:
0.1xe2x89xa6xcex22xe2x89xa680
0.1xe2x89xa6xcex32xe2x89xa680
xcex12+xcex22+xcex32=100
xcex41 less than xcex42xe2x89xa667
In one embodiment of the present invention, the X1 contains at least one selected from the group consisting of Si, Al, Ti, and V.
In another embodiment of the present invention, M1=M2 and X1=X2.
In another embodiment of the present invention, A2 contains O.
In another embodiment of the present invention, assuming that an average thickness of the magnetic layer is T1 and an average thickness of the intermediate layer is T2, the following expressions are satisfied:
2 nmxe2x89xa6T1xe2x89xa6150 nm
0.4 nmxe2x89xa6T2xe2x89xa615 nm
1xe2x89xa6T1/T2xe2x89xa650
In another embodiment of the present invention, the magnetic film satisfies the following expressions:
20 nm less than T1xe2x89xa6150 nm
1 nm less than T2xe2x89xa615 nm
4xe2x89xa6T1/T2xe2x89xa650
at least 50% of magnetic crystal grains included in the adjacent magnetic layers via the intermediate layer spread across the intermediate layer.
A high-resistant magnetic film of the present invention has a composition represented by M xcex1 X xcex2 (N xcex4 O xcex5)xcex3 (where xcex1, xcex2, xcex3, xcex4, and xcex5 represent % by atomic weight; M is at least one magnetic metal selected from the group consisting of Fe, Co, and Ni; X is at least one selected from the group consisting of Mg, Ca, Sr, Ba, Si, Ge, Sn, Al, Ga, and transition metals excluding the M), wherein assuming that a chemical formula when the X forms a nitride with a lowest nitride generation free energy is XNm, and a chemical formula when the X forms an oxide with a lowest oxygen generation free energy is XOn, the high-resistant magnetic film has the following composition range:
xcex1+xcex2+xcex3=100
45xe2x89xa6xcex1xe2x89xa678
xcex4+xcex5=100
1 less than 100xc3x97xcex3/xcex2/(mxc3x97xcex4+nxc3x97xcex5) less than 2.5
the high-resistant magnetic film contains crystal grains, and a shortest diameter of each of the crystal grains is 20 nm or less.
A magnetic multilayer with high resistivity of the present invention includes a magnetic layer and an intermediate layer alternately formed, wherein the magnetic layer includes a high-resistant magnetic film, the high-resistant magnetic film and the intermediate layer have compositions represented by M1m1X1n1A1q1 and M2m2X2n2A2q2, respectively (where m1, n1, q1, m2, n2, and q2 represent % by atomic weight; M1 and M2 are at least one magnetic metal selected from the group consisting of Fe, Co, and Ni; X1 and X2 are at least one selected from the group consisting of Mg, Ca, Sr, Ba, Si, Ge, Sn, Al, Ga, and transition metals excluding the magnetic metal; and A1 and A2 represent at least one selected from the group consisting of O and N), and the high-resistant magnetic film and the intermediate layer satisfy the following expressions:
M1=M2, X1=X2 
q1 less than q2
A method for producing a high-resistant layer of the present invention, includes the steps of: forming a low-resistant layer containing 10% by atomic weight or more of at least one element selected from the group consisting of Mg, Ca, Sr, Ba, Si, Ge, Sn, Al, Ga, and transition metals excluding the M1 on either one of a magnetic thin film and a magnetic layer; and oxidizing or nitriding the low-resistant layer in an atmosphere selected from the group consisting of oxygen, nitrogen, oxygen plasma, and nitrogen plasma.
In one embodiment of the present invention, the magnetic thin film or the magnetic layer contains an element compatible with oxygen.
A magnetic multilayer of the present invention includes a magnetic thin film and a high-resistant layer alternately formed, wherein assuming that an average thickness of the magnetic thin film is T3, and an average thickness of the high-resistant layer is T4 the following expressions are satisfied:
100 nmxe2x89xa6T3xe2x89xa61000 nm
2 nmxe2x89xa6T4xe2x89xa650 nm
10xe2x89xa6T3/T4xe2x89xa6500
In one embodiment of the present invention, the magnetic thin film includes a magnetic layer and an intermediate layer, the magnetic layer, the intermediate layer, and the high-resistant layer have compositions represented by M1X1A1, M2X2A2, and M3X3A3, respectively (where M1 to M3 are at least one magnetic metal selected from the group consisting of Fe, Co, and Ni; X1, X2, and X3 are at least one selected from the group consisting of Mg, Ca, Sr, Ba, Si, Ge, Sn, Al, Ga, and transition metals excluding the magnetic metal; and A1, A2, and A3 are at least one selected from the group consisting of O and N), and the magnetic layer, the intermediate layer, and the high-resistant layer at least satisfy the conditions: M1=M2=M3, and X1=X2=X3.
A thin film head of the present invention includes an upper magnetic pole and a lower magnetic pole, wherein the upper magnetic pole includes either one of a high-resistant magnetic film and a magnetic multilayer with high resistivity, having a specific resistance of 80 xcexcxcexa9cm or more, and either one of a magnetic thin film and a magnetic multilayer, the upper magnetic pole and the lower magnetic pole form a recording gap, and either one of the magnetic thin film and the magnetic multilayer is formed at least in the vicinity of the recording gap at an end of the upper magnetic pole.
In one embodiment of the present invention, either one of the magnetic thin film and the magnetic multilayer is formed at least in the recording gap, and either one of the high-resistant magnetic film and the magnetic multilayer with high resistivity, having a specific resistance of 80 xcexcxcexa9cm or more is formed on either one of the magnetic thin film and the magnetic multilayer.
A method for producing a thin film of the present invention, includes: a first step of moving a substrate onto which a film is formed and a source for supplying material for forming a film in a relative manner; and a second step of forming at least one of a magnetic thin film, a magnetic multilayer, a high-resistant magnetic film, and a magnetic multilayer with high resistivity, wherein at least one magnetization difficult axis of the magnetic thin film, the magnetic multilayer, the high-resistant magnetic film, and the magnetic multilayer with high resistivity is formed in a movement direction in which the substrate and the source are moved in a relative manner.
In one embodiment of the present invention, the movement direction includes a depth direction of an upper magnetic pole of a thin film head.
In another embodiment of the present invention, the first step includes forming a film by a vapor growth method for generating a magnetic field of 50 Oe or more which is substantially orthogonal to the movement direction, substantially parallel to a film formation surface on the substrate, substantially uniform, and substantially in one direction.
In another embodiment of the present invention, the first step includes forming a film by changing a concentration of oxygen, oxygen plasma, nitrogen, or nitrogen plasma in a vapor growth apparatus.
In another embodiment of the present invention, a temperature of the substrate during formation of a film is substantially 300xc2x0 C. or less.
A hard disk drive using the above-mentioned magnetic film as a magnetic pole.
A hard disk drive using the above-mentioned magnetic film as a part of a shield.
A hard disk drive using the above-mentioned high-resistant magnetic film as a magnetic pole.
A hard disk drive using the above-mentioned high-resistant magnetic film as a part of a shield.
A hard disk drive using the above-mentioned magnetic multilayer with high resistivity as a magnetic pole.
A hard disk drive using the above-mentioned magnetic multilayer with high resistivity as a part of a shield.
A hard disk drive using the above-mentioned magnetic multilayer as a magnetic pole.
A hard disk drive using the above-mentioned magnetic multilayer as a part of a shield.
A hard disk drive using the above-mentioned thin film head.
According to an aspect of the present invention, a magnetic film having outstanding soft magnetic characteristics at a high frequency and high Bs can be obtained for the following reason. Magnetic layers are magnetically separated by an intermediate layer, whereby the magnetic layers disposed via the intermediate layer decrease domain wall energy due to their magnetostatic binding or the intermediate layer suppresses the growth of magnetic crystal grains so as to refine them. Thus, apparent crystal magnetic anisotropy is decreased (so-called refining effect), which enhances soft magnetic characteristics.
Furthermore, even in the case where the thickness and width of a film have a high aspect ratio during refining of the film, shape anisotropy magnetic energy in a direction perpendicular to the film is suppressed, so that outstanding high-frequency characteristics can be exhibited. Particularly, in the case where a magnetic film of magnetostatic binding type is used in the vicinity of a recording gap of an upper magnetic pole of a thin film head, the magnetization of magnetic layers separated by an intermediate layer causes magnetostatic binding on the side face of the magnetic pole, and is likely to be directed in a preferable magnetization direction similarly to the case where apparent uniaxial anisotropy is formed; therefore, high-frequency characteristics are enhanced without conducting heat treatment in a magnetic field or forming a film in a magnetic field.
M1 may be any of Fe, a FeCo alloy, and a FeCoNi alloy. X1 contained in a magnetic layer has at least one effect such as enhancing corrosion resistance, refining crystal grains of magnetic metal, decreasing crystal magnetic anisotropy of magnetic crystal grains, and decreasing magnetostriction, as long as its amount is at least about 0.1%. Zn, Pt, Rh, Ru, and the like enhance corrosion resistance, Cr, Ge, Ga, V, Al, Si, Ti, and Mo decrease crystal magnetic anisotropy, and Ti, Si, and Sn decrease magnetostriction, for example, in the case where M1 is Fe. Although one kind of M1 has an effect, two or more kinds of M1 will have more remarkable effect of decreasing a crystal grain diameter. Furthermore, the addition of Al further decreases a crystal grain diameter, which has an effect of enhancing soft magnetic characteristics. If xcex21 is more than about 12%, and xcex41 is more than about 10%, Bs is decreased, which is not preferable.
An intermediate layer contains transition metal. Therefore, even when RIE involving generation of carbonyl of transition metal is used, a fine pattern can be relatively easily formed. In terms of processability, it is preferable that transition metal such as Cr and Pt is used for an intermediate layer. In terms of suppressing an eddy current loss between layers, a high-resistant oxide such as SiO2Al2O3 is preferably used. The intermediate layer of the present invention uses an oxide, a nitride, or material consisting of an oxide and a nitride having relatively small energy of dissociation, so that the intermediate layer allows a high resistance to such a degree as to realize relatively satisfactory processability and sufficiently suppress an eddy current.
Furthermore, X2 contained in the intermediate layer forms a reactive product with A2 to promote separation from the magnetic layer. X2 also has an outstanding effect on magnetostatic binding and refining crystal grains, even in the case where the intermediate layer of the present invention has a composition or a thickness which does not suppress an eddy current. X2 exhibits its effect in an amount of about 0.1% or more. When the amount is more than about 80%, processability for patterning to a fine shape becomes poor or magnetic degradation is caused due to internal stress or strain.
It is required that xcex42 contains an O or N concentration higher than that of 67 1. When the xcex42 concentration exceeds about 67%, excess oxygen or nitrogen gas is discharged from the intermediate layer in the course of heat treatment at a temperature higher than a film formation temperature, which may damage a film. Thus, the xcex42 concentration is about 67% or less.
In the magnetic thin film with the above-mentioned structure where M1=M2 and X1=X2, by using an intermediate layer having the same element as that of the magnetic layer, interface energy occurring between the intermediate layer and the magnetic layer is suppressed. Therefore, magnetoelastic energy caused by internal stress generated on the interface and anisotropy energy in the film can be decreased. As a result, a magnetic film having outstanding soft magnetic characteristics and high Bs can be obtained. Furthermore, in the case where the intermediate layer of the magnetic thin film with the structure of the present invention has a thickness sufficient for realizing magnetostatic binding, vertical magnetization generated by interface strain can be suppressed; therefore, a domain structure is realized in which magnetostatic binding works more effectively.
Furthermore, interface energy is relatively low. Therefore, it is not required to form a film at a high temperature for the purpose of removing strain energy during film formation or after film formation, or to conduct heat treatment for removing strain at a high temperature. This allows soft magnetic characteristics to be easily obtained by a process at a low temperature (about 300xc2x0 C. or less). Furthermore, in the case where layers of different materials are formed, when materials with low interface energy are combined, inter-layer peeling is likely to be caused. However, according to the present invention, the element common to the magnetic layer and the intermediate layer functions as glue, so that the layered film of the present invention has high strength. Furthermore, since M1=M2 and X1=X2 are satisfied, in the case where a vapor deposition, for example, is used, one source for supplying film formation material suffices to easily form a film. In the case of the structure of the present invention, even when the composition of each magnetic layer and intermediate layer is continuously varied, the same effect can be obtained.
According to another aspect of the present invention, X2 contained in the intermediate layer is capable of easily generating a reaction product with A2, due to its low oxide generation free energy. Thus, even when the intermediate layer is relatively thin, it has appropriate separation effect between the magnetic layers.
According to still another aspect of the present invention, at least one selected from the group consisting of Rh, Ru, and Pt is added to the magnetic layer and the intermediate layer, respectively, whereby corrosion resistance of thin film material is remarkably enhanced. The content of these elements of about 0.1% or more is effective, whereas the content of about 8% or more will decrease a saturated magnetic flux density, and degrade soft magnetic characteristics.
Furthermore, in the magnetic thin film with the above-mentioned structure in which X1 is at least one selected from the group consisting of Si, Al, Ti, and V, in the case where a trace amount of Si, Al, Ti, and V is contained in crystal grains included in the magnetic layer, crystal magnetic anisotropy energy is decreased. This results in a refining effect and a decrease in domain wall energy. Thus, more outstanding soft magnetic characteristics can be obtained. When these elements react with O or N in the magnetic layer, the growth of crystal grains is suppressed, and a refining effect is enhanced. In the case where these elements are contained in the intermediate layer, since any of these elements has large free energy for generating an oxygen or a nitrogen and has a large diffusion constant, the intermediate layer can be effective with a relatively small thickness. Such a relatively thin intermediate layer allows the magnetostatic binding between the magnetic layers to strengthen; therefore, a decrease in domain wall energy is large, and a decrease in a saturated magnetic flux density in the entire film caused by the intermediate layer is small.
In the magnetic thin film with the above-mentioned structure in which A2 contained in the intermediate layer is O, the intermediate layer has particularly high thermal stability. Therefore, for example, even in the case where a heat treatment temperature in a magnetic field required for fixing an antiferromagnetic film of a spin valve film in an operation environment of an HDD is relatively high, soft magnetic characteristics will not degrade.
According to still another aspect of the present invention, outstanding soft magnetic characteristics and high Bs can be obtained. This may be because soft magnetic characteristics are exhibited by a kind of refining effect of magnetic crystal grains.
The magnetic layer is composed of crystal grains containing a trace amount of amorphous material, and adjacent magnetic layers are not required to be completely separated by the intermediate layer. Even when crystal grains in the magnetic layers interposing the intermediate layer therebetween are observed to be partially continued crystallographycally, magnetic strength of crystal grains of in-plane portions of the film is different from that in a direction perpendicular to the film passing through the intermediate layer.
Therefore, even when the magnetic thin film is refined, for example, as a magnetic pole of a thin film head, outstanding soft magnetic characteristics can be exhibited at a high frequency without being influenced by shape anisotropy in a direction perpendicular to the film. Soft magnetic characteristics become particularly outstanding, when the intermediate layer is composed of amorphous material or microcrystal containing amorphous material. When the thickness of the magnetic layer is about 2 nm or less, magnetic characteristics degrade. When the thickness of the magnetic layer is about 20 nm or more, grains are likely to excessively grow. Furthermore, unless the thickness of the intermediate layer is about 0.4 nm or more, crystal grains cannot be effectively refined. Unless the thickness of the intermediate layer is about 2 nm or less, soft magnetic characteristics degrade. This may be because exchange binding between the magnetic layers is weakened. Furthermore, in terms of Bs, the ratio of film thickness is preferably 1xe2x89xa6T1/T2xe2x89xa650.
According to still another aspect of the present invention, high Bs as well as outstanding soft magnetic characteristics at a high frequency can be obtained. This may be because of a kind of magnetostatic binding effect. The magnetic layer is composed of crystal grains or crystal grains containing a trace amount of amorphous material.
The magnetic layers are not required to be electrically insulated by the intermediate layer. When the thickness of the magnetic layer is about 20 nm or less, or larger than about 150 nm, magnetostatic binding becomes less effective. When the thickness of the intermediate layer is about 2 nm or less, the magnetic layers cannot be sufficiently separated, and exchange binding therebetween becomes strong. When the thickness of the intermediate layer exceeds about 15 nm, the distance between the magnetic layers becomes large, which results in that sufficient magnetostatic binding is unlikely to occur. If the shortest diameter of crystal grains included in the magnetic layer is about 20 nm or less which is sufficient for allowing a refining effect, in addition to magnetostatic binding, soft magnetic characteristics are further enhanced. The above-mentioned preferable thickness is considered to be determined in such a manner that the total of magnetostatic energy (which decreases due to magnetostatic binding of the magnetic thin film in a composition range of the present invention) and various energies (which are related to a domain structure resulting from a multi-layer structure). In terms of Bs, the ratio of film thickness is preferably 4xe2x89xa6T1/T2xe2x89xa650.
According to still another aspect of the present invention, a high-resistant layer has an effect of suppressing an eddy current, and compositions of the magnetic layer, the intermediate layer, and the high-resistant layer are close to each other. Therefore, interface energy occurring on an interface between different kinds of layers can be suppressed. This will decrease magnetostriction multiplied by strain energy, caused by an internal stress occurring on the interface, and anisotropic energy in the film.
Consequently, a magnetic film having outstanding soft magnetic characteristics and high Bs can be obtained even in the case where the total thickness is relatively large. Furthermore, interface energy is relatively low. Therefore, it is not required to form a film at a high temperature for the purpose of removing strain energy during film formation or after film formation, or to conduct heat treatment for removing strain at a high temperature. This allows soft magnetic characteristics to be easily obtained by a process at a low temperature (about 300xc2x0 C. or less).
Furthermore, in the case of using vapor deposition, depending upon the composition of the magnetic film of the present invention, one source for supplying a film formation material suffices. Therefore, high-speed film formation can be conducted with a simple apparatus and satisfactory mass-productivity. Furthermore, in the case where layers of different materials are formed, when materials with low interface energy are combined, inter-layer peeling is likely to be caused. However, according to the present invention, the element common to the magnetic layer and the intermediate layer functions as glue, so that the layered film of the present invention has high strength.
According to the present invention, a high-resistant layer of a magnetic multilayer with the above-mentioned structure is produced by forming a low-resistant layer containing at least one selected from the group consisting of Mg, Ca, Sr, Ba, Si, Al, Ti, and Cr in an amount of about 10% by atomic weight or more on a magnetic thin film or a magnetic layer, and oxidizing or nitriding the low-resistant layer in an atmosphere of oxygen/oxygen plasma or nitrogen/nitrogen plasma. Thus, a high-resistant layer with a relatively small thickness and outstanding insulation can be produced. The low-resistant layer may be formed of either of Si, Al, Ti, and Cr, or may be formed of an alloy film thereof. Even when the low-resistant layer is formed of an alloy with magnetic transition metal such as Fe, an excellent high-resistant layer can be produced, as long as at least one of Mg, Ca, Sr, Ba, Si, Al, Ti, and Cr is contained in an amount of about 10% by atomic weight or more. A relatively thin insulation layer has outstanding magnetostatic binding characteristics, so that both high soft magnetic characteristics and outstanding high frequency characteristics can be obtained.
Furthermore, in a thin film head having a structure in which at least an upper magnetic pole is composed of a high-resistant magnetic film or a magnetic multilayer with high resistivity, having a specific resistance of about 80 xcexcxcexa9cm or more and a magnetic thin film or a magnetic multilayer with the above-mentioned structure, and the magnetic thin film or the magnetic multilayer is formed at least in the vicinity of a recording gap at an end portion of the upper magnetic pole, outstanding overwrite characteristics are exhibited at a high frequency even at a relatively low recording current. This is because of the following: high Bs material of the present invention is used for the end portion of the recording gap of a recording head in the upper magnetic pole where a magnetic flux with its core width narrowed is likely to be saturated, and a high-resistant magnetic film or a magnetic multilayer with high resistivity having a small loss of an eddy current is used for another portion of the upper magnetic pole for inducing a magnetic flux into the end portion of the recording gap.
The high-resistant film may be a layered film of a high-resistant layer and a magnetic layer, or may be a high-resistant single film in which a grain boundary of microcrystal grains considered to be granular is substantially surrounded by high-resistant amorphous material. It is important that the high-resistant film is a soft magnetic film with a specific resistance of about 80 xcexcxcexa9cm or more. When the present invention is applied to a lower magnetic pole as well as the upper magnetic pole, a recording current can be further decreased.
Furthermore, a thin film head with the above-mentioned structure, in which a magnetic thin film or a magnetic multilayer with the above-mentioned structure is formed at least on a recording gap, and a high-resistant magnetic film or a magnetic multilayer with high resistivity having a specific resistance of about 80 xcexcxcexa9cm or more is formed on the magnetic thin film or the magnetic multilayer, exhibits outstanding overwrite characteristics at a relatively low recording current. Such a thin film head can be produced by a simple process. The high-resistant film herein should also be a soft magnetic film with a specific resistance of about 80 xcexcxcexa9cm or more.
According to still another aspect of the present invention, a thin film head having outstanding high-frequency characteristics can be produced. This is because of the following: high-resistant material having the composition and structure of the present invention can suppress an eddy current loss, so that recording ability at a high frequency can be remarkably improved. A specific resistance of about 80 xcexcxcexa9cm or more is caused by a high-resistant X-O or N compound formed in a magnetic crystal grain boundary.
Furthermore, it is important that O and N should be contained in a range required for forming an X-O or N compound, represented by the above-mentioned expression. Soft magnetic characteristics are caused by microcrystal grains having the shortest diameter of about 20 nm or less. The microcrystal grains have a structure close to a needle-shape or a grain-shape.
According to still another aspect of the present invention, a thin film head having outstanding high-frequency characteristics can be produced. The above-mentioned high-resistant thin film comprises microcrystals having the shortest diameter of about 20 nm or less or comprises microcrystal and amorphous material. Therefore, a number of crystal grain boundaries are formed, and as a result, crystal grains do not move smoothly because of domain walls, and a domain wall resonance loss is increased.
However, in a layered structure of the present invention, a domain wall structure is changed so that magnetostatic energy of the entire film is decreased; as a result, domain wall energy is decreased, and a domain wall resonance loss at a high frequency is decreased. Furthermore, in the case where, due to a leakage magnetic field from the high-resistant magnetic film, magnetostatic binding occurs in the high-resistant magnetic film and in the magnetic thin film or the magnetic multilayer included in the upper magnetic pole, magnetostatic energy over the entire thin film head is decreased and high-frequency characteristics are enhanced.
Furthermore, since the composition of the magnetic layer is close to that of the intermediate layer, interface energy occurring on an interface between different kinds of layers can be suppressed. This will decrease magnetostriction multiplied by strain energy, caused by an internal stress occurring on the interface, and anisotropic energy in the film. Furthermore, in the case of using vapor deposition, depending upon the composition of the high-resistant magnetic film of the present invention, one source for supplying a film formation material suffices. Therefore, high-speed film formation can be conducted with a simple apparatus and satisfactory mass-productivity.
Furthermore, according to the present invention, a magnetic thin film (or magnetic multilayer) and a high-resistant magnetic film (or magnetic multilayer with high resistivity) are formed by vapor deposition while a positional relationship between a substrate and a source for supplying film formation material is changed during film formation, and a magnetization difficult axis of a thin film is formed in the direction of relative movement between the substrate and the source. In this method, uniaxial magnetic anisotropy formed in the thin film is determined mainly by a growth direction of magnetic crystal grains included in the magnetic film and the diameter of a fine crystal grain. Therefore, for example, even in the case where a heat treatment for fixing an antiferromagnetic film of a spin valve film in an operation environment of an HDD is conducted while a magnetic field is applied in a direction orthogonal to a direction of a magnetization easy axis of the magnetic thin film (or the magnetic multilayer) and the high-resistant magnetic film (or the magnetic multilayer with high resistivity), anisotropy is unlikely to be disturbed.
According to a method for producing a thin film for a thin film head in which a direction of relative movement is in a depth direction of an upper magnetic pole of the thin film head, a magnetization difficult axis which is stable against heat treatment is formed in the depth direction of the upper magnetic pole, and the film quality on a slope surface of the upper magnetic pole is improved. Therefore, a thin film head having outstanding recording characteristics can be produced.
In a magnetic thin film (or magnetic multilayer), a high-resistant magnetic film (or magnetic multilayer with high resistivity), and a thin film head with the above-mentioned structure formed by using a vapor growth method for generating a magnetic field of about 50 Oe or more which is substantially orthogonal to the movement direction, substantially parallel to a film formation surface on the substrate, substantially uniform, and substantially in one direction, the intensity of uniaxial anisotropy of the magnetic thin film (or the magnetic multilayer) and the high-resistant magnetic film (or the magnetic multilayer) is averaged. Thus, high-frequency characteristics are stabilized over the entire thin film head.
According to still another aspect of the present invention, a magnetic layer and an intermediate layer of a magnetic thin film; a magnetic layer, an intermediate layer, and a high-resistant layer of a magnetic multilayer; and a magnetic layer and an intermediate layer of a high-resistant magnetic film or a magnetic multilayer with high resistivity can be produced by using the same source for supplying film formation material. Therefore, a vapor growth apparatus can be miniaturized, and films can be formed at a high speed.
Furthermore, according to a method for producing a magnetic thin film, a magnetic multilayer, a high-resistant magnetic film, a magnetic multilayer with high resistivity, and a thin film head with the above-mentioned structure in which a substrate temperature is substantially about 300xc2x0 C. or less, even a very thin intermediate layer (which cannot be used at a high temperature of about 500xc2x0 C.) can be used. Because of a relatively low production temperature (about 300xc2x0 C. or less), such a very thin intermediate layer does not have its structure changed due to heat diffusion. The very thin intermediate layer allows the strongest magnetostatic binding between magnetic layers disposed via the intermediate layer, as long as the magnetic thin film is of a magnetostatic binding type with the above-mentioned structure. Also, a very thin high-resistant layer which does not allow Bs to decrease can easily be formed. With a high Bs composition (i.e., with a composition in which a metal magnetic element ratio is large), crystal grains are likely to grow by heat treatment. However, since a production temperature is relatively low, crystal grains can easily be maintained in a fine state, and a magnetic thin film or a magnetic multilayer using the above-mentioned refining effect can easily be realized. Because of this, high Bs, a high resistance, and outstanding high frequency characteristics are realized, and a thin film head with high corrosion resistance caused by microcrystal and/or amorphous material can be provided.
Furthermore, in an HDD using, at least for a magnetic pole or a part of a shield, a magnetic thin film, a magnetic multilayer, a high-resistant magnetic film, or a magnetic multilayer with high resistivity having the above-mentioned structure, and in an information processing apparatus using such an HDD, a high recording density can be realized at a frequency of about 100 MHz or more. Thus, an apparatus can be miniaturized and rendered light-weight.
Furthermore, in an HDD using a thin film head with the above-mentioned structure and in an information processing apparatus using such an HDD, in addition to miniaturization of an apparatus and rendering an apparatus light-weight due to a high recording density, a power consumption can be reduced due to a decreased recording current. As a result, a battery of a portable information processing apparatus provided with the HDD can be miniaturized, and such a portable apparatus can be used continuously for a longer period of time.
Thus, the invention described herein makes possible the advantages of providing a soft magnetic material with high BS having outstanding high frequency characteristics and a method for producing the same.